It is previously known to use different types of suction pumps at the suction drainage of body cavities with regard to body liquid accumulated therein after a surgical incision. One such known pump is a bellows pump made of a polymeric material, which pump after having been compressed endeavors to stretch out again, to expand, whereby a vacuum is created in a drainage tube connected to the bellows pump. When the pump has reassumed its original shape and contains drained liquid it can be recompressed, whereby liquid drained is pressed out through a further tube connected to the pump. It has turned out that the bellows pump thus known in the art provides a decreasing vacuum in the drainage tube, which in turn leads to an unacceptable reduced transport of accumulated liquid.
One has thus requested a suction pump which provides a more constant vacuum during its whole period of action. One has also wished to have a suction pump which is smaller and easier to handle than that known one, as it has turned out that this is difficult to hide in the clothes, and, further demands a careful instruction in order to be handled. Correctly handled the known device is per se simple to handle.